Wireless communication systems provide several important advantages over conventional telephone systems. First, wireless communication users can communicate in locations where conventional telephone service is not available, for example in remote or particularly rugged locations. Second, wireless communications users have much more mobility because they don't have to connect to a fixed network of telephone lines. These and other favorable characteristics make wireless communications ideally suited for search and rescue, law enforcement and a myriad of other uses, including everyday use. Two of the most common approaches for providing wireless communications are two-way radios and cellular telephone systems.
In their most simplistic form, two-way radios are portable frequency-modulated (FM) transceivers that allow users to both transmit and receive FM signals directly to and from other users. Two-way radios are relatively simple, are inexpensive to manufacture, are easily miniaturized and provide relatively robust performance and mobility over reasonable distances. Examples of two-way radios include citizen band (CB) radios and "walkie talkies" such as Motorola Corporation's TalkAbout.RTM. radios.
Despite the benefits of two-way radios, they have several drawbacks. First, two-way radios typically support only half-duplex operation, meaning that only one user can talk at a time. A user must push a "talk" button to talk to another user and if both users push their "talk" buttons at the same time, then the users cannot hear each other. The reason for this is that all participants transmit data on the same channel. Two-way radios also require that users agree upon and select a particular channel to use for a conversation. If the channel being used is lost or cannot be used because of excessive interference, then the users must transfer to a different channel which can be difficult to do unless an alternate channel has been previously agree upon. Another problem with two-way radios is that communications are generally not private. Anyone with a compatible radio can eavesdrop on a conversation simply by tuning their radio to the channel on which the conversation is being held. Finally, two-way radios do not provide the call services available with digital systems such as call waiting, caller identification and messaging.
Cellular telephone systems are based upon a network of base stations that provide a coverage area in which users can communicate. Users communicate indirectly with other users through the base stations. Digital cellular telephone systems generally provide superior voice quality and are more secure than analog cellular telephone systems and two-way radios. Furthermore, digital cellular telephone systems provide a wide variety of call services such as call waiting, call forwarding and voice mail, that are not available on analog cellular telephone systems and two-way radios.
Notwithstanding the advantages that digital cellular telephone systems provide over analog cellular telephone systems and two-way radios, they also have some drawbacks. One drawback is that users can only communicate within the coverage area of the cellular network. Cellular telephone system coverage is typically provided only in metropolitan areas and is not available in remote areas where it is less economically feasible to install the necessary infrastructure. Another problem with cellular telephone systems is that users must pay for "air time" to connect to public service telephone networks (PSTNs).
Based on the need for wireless communications and the limitations in the prior approaches, an approach for providing wireless communications that does not suffer from the limitations of the prior approaches is highly desirable.